Also, if we allowed the RP weapon policy to be smacked away by the "I looted it", imagine the pvp-whores who would run around... Sabres with Krakens, Tizonas and worse. GMG using Krakens and Tizonas on Eagles. Even Raven Claws with 8 krakens and an inferno (wouldn't work, but still).
It would lead to such madness...
Think about Xing and Jinx's points. Just because in-game stats say its better, doesn't mean you should use it. Your characters wouldn't know how to use nor how to maintain foreign weaponry.
Edit: Why are you complaining about Shield Busters? Adv/Imp debilitators are better than tizonas, you can actually see where the shots are going and they have a higher speed. Plus, they won't get you sanctioned...